Linear guides are often provided with a length measuring device so that a guide carriage guided longitudinally displaceably on the guide rail can be positioned satisfactorily by suitable drive and control means. DE 102 14 426 A1, for example, discloses a guide rail. The material measure arranged laterally next to the guide rail is held on the guide rail via a holder. The holder provides two approximately u-shaped brackets which are fastened in each case to one end of the material measure and which surround the guide rail. The u-shaped holding brackets, surrounding the guide rail, are braced with the latter, and the guide surfaces of the guide rail act as tension surfaces to releasably fasten the holding brackets. One disadvantage of a holder of this type may be seen in that a further guide carriage which is arranged on the guide rail is limited in its longitudinal displaceability by the arrangement of the two holding brackets which surround the guide rail.